Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
1996-09-09
2001-05-29
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C156S345420
Reexamination Certificate
active
06239038
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the surface preparation of objects with fine surfaces such as semiconductor wafers and particularly to a method and apparatus for both wet and dry processing of such wafers.
BACKGROUND OF THE INVENTION
Microelectronics processing is a matter of surfaces. Processing techniques are concerned with modifying properties less than a few microns below or above the surface of a substrate material. Present complex electronic integrated circuits are formed by using planar processes in which an ultraclean, flat wafer of silicon is used as a substrate upon which a large number of identical devices are built by various oxidation, photolithography, removal, ion bombardment and deposition processes. Therefore, the integrated circuit manufacturing is essentially a sequence of chemical processes.
An ultraclean surface preparation before and after the processes necessary for the patterning of microelectronics devices is now more important than ever before as the surface diameter extends toward 300 mm. and the structure dimension shrink below microns. It is well known that the device performance, reliability and product yield of silicon circuits are critically affected by the presence of chemical contaminants and particulate impurities on the wafer of device surface.
Current existing methods for ultraclean surface preparation can be divided into two main categories: wet processes, such as immersion and spray techniques, and dry processes such as chemical vapor and plasma based techniques.
Wet processing consists of a series of steps of immersing or spraying the wafers with appropriate chemical solutions. The wet processes for ultraclean wafer surface preparation has been successfully used for the past twenty-five years and are still the predominant methods used in manufacturing circuits. However, the high cost of the large amount of ultrapure chemicals required in the current wet processes and the treatment of hazardous waste resulting from the processes, together with its incompatibility with the advanced concepts of integrated processing such as cluster tooling, are the main reason for searching for gas processing methods that are less affected by these limitations.
Although dry processing has shown several advantages in the chemical processing of advanced sub-micron features integrated circuits with high aspect ratio structures, numerous advantages of wet chemical processing often outweigh their “generic” problems in many production applications.
There is a real need in today's semiconductor fabrication industry to tailor the chemical processes to minimize the manufacturing costs in order to remain competitive in the ever increasing demands of the semiconductor market, while at the same time, to meet the increasing quality demands of the devices. The best answer for that is to combine the wet and dry techniques into the processes.
Thus, there is a need of a method and apparatus for the ultraclean surface preparation that is capable of performing both wet and dry chemical processes.
There is also a strong need for a method and apparatus to reduce chemical consumption, to reduce processing steps, and to increase equipment utilization without losing the effectiveness of the process.
There is further need for a method and a system that can be fully automated, well controlled, and integrated with cluster tool environments.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus capable of either liquid or gas processing of semiconductor wafers or other objects having fine surfaces.
The apparatus of the invention includes an enclosed housing of a material unaffected by the chemicals used in the process. The housing has an internal cavity that contains a rotatable and vertically movable upper plate having apertures for either admitting chemical fluids or to apply a vacuum for venting the housing or for grasping a wafer which is positioned between the upper plate and a lower plate having apertures appropriately placed in its surface for admitting processing fluids and drying gas.
The preferred method is to force a thin layer of processing fluid, either gas or liquid, through the narrow space between the surfaces of a semiconductor wafer and plates of the processing apparatus. While the fluid passes through the narrow space, it contacts and interacts both chemically and physically with the semiconductor wafer surfaces. The narrow space may be from 0.01 mm. to 10 mm, depending on the nature of the chemical processes.
In a preferred embodiment, the particular choice of spacing will be one where an optimum fluid flow is created to simultaneously bring fresh chemicals into contact with the surface of the semiconductor wafer and remove unwanted reaction products away from the surface of the semiconductor wafer toward the drain in order to prevent the unwanted reaction products from redepositing on the surface of the semiconductor wafer. In this regard, the chemical flow can be turbulent or laminar, depending on the nature of the process being carried out. In the preferred embodiment, the particular choice of narrow space will additionally result in the desired processing of the semiconductor wafer surface using a minimum of chemicals, as well as minimize the costs of treating the resulting hazardous wastes.
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Christensen O'Connor Johnson & Kindness PLLC
Deo Duy-Vu
Utech Benjamin L.
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